The present disclosure relates to network computing. Computer networks typically include a collection of computing devices enabled to communicate with each other for handling data traffic and control instructions. For example, such devices can include servers, data centers, routers, network switches, management applications, wireless access points, and client computers. Computer networks can provide network connectivity to wired computing devices and/or wireless computing devices. Most of current generation computer networks employ special purpose appliances called Wireless Controllers for managing wireless client devices. Such environment is called overlay networks to indicate that wireless is overlaid on top of wired. Certain computer networks can provide an environment in which both wired and wireless users are supported by a same set of network switches. Such an environment can be described as a unified network.
Computer networks can include various configurations. One such configuration, known as a local area network (LAN), provides network connectivity to a group of client computers. This group is typically small relative to other networks, and is often limited to a specific geographical area or network switch. A wireless local area network (WLAN) allows computing devices to move around within a local area and maintain network connectivity. A virtual local area network (VLAN) enables a group of client computers to communicate and access specific resources as members of a given domain even if the various member client computers are not attached to the same network switch.
Wireless Local Area Networks (WLANs) are a popular and inexpensive way to allow multiple users of “mobile units” (MUs) to communicate with each other, to access a wired LAN, to access a local server, to access a remote server, such as over the Internet, etc. A wireless local area network (WLAN) typically includes an Access Point (AP), Wireless Controller and one or more mobile units. Each mobile unit may be a device such as a notebook computer, personal digital assistant (PDA), wireless VoIP telephone or the like that transmits radio signals to and receives radio signals from other devices in the local area network via the AP. The mobile unit includes a wireless transceiver which can communicate with an access point. The communication can occur via radio waves, infrared, or any other known form of wireless communication. The access point allows wireless mobile units to communicate with each other and to communicate with infrastructure connected to the access point.
The server can provide services, such as access to applications like an email system, a word processing program, an accounting system and/or a dedicated database. Wireless LANs are employed within such facilities as businesses, university classrooms or buildings, airport lounges, hotel meeting rooms, residences etc. When a user is physically located in the vicinity of an access point, the transceiver of the mobile unit communicates with the access point and a connection to the wireless LAN is established with approval from the Wireless Controller.
APs and mobile units transmit data in units referred to as frames over a shared-communications channel. Frames transmitted from a mobile unit to an AP are referred to as uplink frames, and frames transmitted from an AP to a mobile unit are referred to as downlink frames. In a situation where two or more mobile units (or an AP and a mobile unit) transmit frames simultaneously, then one or more of the frames can become corrupted, referred to as a collision. As a result, Wireless Local Area Networks (WLANs) typically employ one or more protocols to ensure that a mobile unit or AP can gain exclusive access to the shared-communications channel for a predetermined interval of time in order to transmit its frames without collisions occurring.
Certain wireless network protocols (e.g., Institute of Electrical and Electronics Engineers [IEEE] 802.11, etc.) provide for the AP to periodically broadcast a special frame called a beacon that can be heard by the mobile units in the BSA (basic service area), the area covered by the AP. The beacon contains a variety of information that enables the mobile units to establish and maintain communications in an orderly fashion, such as a timestamp, which enables mobile units to synchronize their local clocks, and signaling information (e.g., channel number, frequency hopping pattern, dwell time, etc.).